I don’t think anyone is saying roaming would be the solution to major outages like yesterday’s. But had it been in operation yesterday, it could have significantly reduced the extent of the impact for the users.
Businesses that couldn’t use their mobile-connected EFTPOS terminals yesterday would’ve been able to stay online (and I suspect that those terminals don’t use a lot of network bandwidth, so I don’t see that type of switchover swamping the receiving networks). People with personal alarms that depend on mobile connectivity wouldn’t have been at risk. Emergency services could’ve called people back. And so on.
Whether or not the outage resulted from a change made in the middle of the night, I agree with your description of the effect that a core network outage has on the support team’s ability to become aware of and start doing anything about the outage.
Contingency plans for such situations must exist and have been proven to take such issues into account - as Disaster Recovery Planning is supposed to do.
For example, are the support people certain to be able to get into the data centre when they do get there? Do the contingency plans make sure those who have or can grant access to the data centre will be contactable if this network is down, for example? It’s not much use if all the emergency contact numbers are mobiles that depend on this network …
